Zone 3: The trunk
The trunk (or stem) of the tree is the main supporting structure that holds up the branches.
Sometimes an excessive trunk lean can cause a tree to fall. See the section “Leaning Trees” to learn more about leans.
Absence of bark on the trunk can indicate a dead section or a fungus attack. Large areas of the trunk that do not have bark indicate a larger section of dead wood and thus increased risk of tree failure.
A long streak of missing bark coming down the trunk usually means lightning has hit the tree. Use binoculars to look into the treetop for cracked, shattered and/or broken branches.
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Lightning strike on pine tree
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Borer frass
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Pitch tubes on pine trunk
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Weak trunk connection
If insects attack a tree’s trunk, you will probably see frass, the fine light-colored sawdust shavings like the borer frass at left. In pine trees, the presence of “pitch tubes” resembling little balls of light colored sap about the size of a marble is a sign of beetle attack. Expect to see dead branches in the crown (if not an entire dead top) if insects are present, because they or their larvae often block the flow of water to the treetop.
In double- or triple-trunk trees, the points where the multiple trunks connect must be inspected for weakness or storm damage. Weak connections are usually evidenced by a tight “V” shape, similar to the junction here. Look closely to see if there are any visible cracks in this area. Sometimes you’ll see an unusual ridge of wood growing down from the intersecting V connection, usually on both sides. This is a sign of an old crack under the surface or the tree’s effort to strengthen the weak area. It’s best not to climb in trees with these formations because they are more prone to splitting, and they will snag your throwlines. If you do climb trees with these formations, climb on the sections that are more vertical and avoid sections that lean outward. Watch for branches that have these weak connections, as they, too, are prone to breakage.
